This invention relates to constant velocity joints of the type used to transmit torque at a constant velocity between two shafts through an angle.
A typical constant velocity joint used to transmit torque between two shafts through an angle includes an outer race fixed to one of the shafts and having an inner part-spherical surface, an inner race disposed in the outer race and having an outer part-spherical surface spaced from the inner surface of the outer joint member, a plurality of axially extending, circumferentially spaced ball grooves that face one another and have centers of curvature which are axially offset on opposite sides of a center point of the joint defined by a common center of the inner and outer joint surfaces, and a plurality of torque-transmitting balls corresponding in number to the number of grooves sets and disposed one each in the opposing groove sets to enable angulation of the shafts while precluding relative rotation of the inner and outer races to effect transmission of torque through the joint. An annular ball cage is disposed in the gap between the inner and outer joint members and serves to guide the inner and outer surfaces of the joint members during angulation and to capture the balls within the grooves. Typically, the number of balls in corresponding group sets corresponds to either 6 or 8 in number.
Constant velocity joints of the general type described above are used in many automotive front wheel drive applications and have proven to be an effective, robust design. However, because of the many parts and surfaces to machine, such joints can be costly to manufacture.
It is an object of the present invention to provide a simplified constant velocity joint construction that eliminates many of the complex component parts and machined surfaces, while enabling the transmission of torque between two shafts through an angle of the joint.
A constant velocity joint constructed according to a presently preferred embodiment of the invention includes an outer race coupled to a first shaft and having a socket with a part-spherical inner surface, an inner race coupled to a second shaft and having a part-spherical outer surface engaging the part-spherical inner surface to provide relative angular movement of the races about a common joint center of the races. The joint includes torque-transmitting structure acting between the races to prevent relative rotation of the races for effecting transmission of torque between the shafts. Such torque-transmitting structure includes a single functional ball groove formed in the inner surface of the outer race and a single complementing ball groove formed in the outer surface of the inner race, together with a single torque-transmitting ball disposed in the grooves and urged by the grooves under torque load toward an axially end of the outer race. A retainer acts on the ball to maintain the ball within the grooves.
One advantage of the present invention is that a constant velocity joint is provided which eliminates the need for all but a single functional ball groove set, thus reducing machining costs and the time it takes to machine the races.
The present invention has the further advantage of providing a single functional torque-transmitting ball which is received in the single functional groove set which enables angulation of the races while eliminating relative rotation of the joints to effect the transfer of torque through the joint, thus further reducing the cost and complexity of the joint.
The invention has the further advantage of eliminating the usual ball cage that is typically carried between the inner and outer race and formed with a number of windows for capturing a plurality of balls. The elimination of the ball cage further simplifies the construction and reduces the cost of manufacturing constant velocity joints.
A constant velocity joint constructed according to the present invention is particularly useful in applications where the joint is subjected to low torque load and low angulation. In such applications, there is no need to provide numerous ball grooves sets and balls and a ball cage to hold them in place according to the present invention, which achieves the functionality of traditional constant velocity joints but by means of a much simpler construction.